In recent years, with the development of a ubiquitous society, electronic apparatuses such as information processing apparatuses (servers, workstations, PCs, game consoles, etc.) and communication apparatuses (cellular phone, etc.) have improved in a signal transmission rate due to the optical/electric conversion of an optical module and have been miniaturized. Moreover, high speed, multi-functionality, and complexity of MPUs (Microprocessor Units) have been realized in servers, workstations, PCs, cellular phones, and game consoles. High speed has been realized in recording apparatuses (memory, etc.).
However, a problem with a malfunction in these apparatuses or other electronic apparatuses may arise due to a noise transmitted from these apparatuses or a noise caused in a conducting member of an apparatus. Examples of the noise include a noise caused due to impedance mismatch with a signal transmission line of a wiring circuit board in a laser diode, a photodiode, the MPU, an electronic component, or the like, cross talk between signal transmission lines, and a noise caused by parallel plate resonation between a power supply line and a ground layer by simultaneous switching of a semiconductor device such as the MPU.
The following wiring circuit boards were suggested to suppress these noises:
(i) a wiring circuit board which includes a power supply layer and a ground layer used to supply a power source to electronic components mounted on the surface thereof, wherein the power supply layer is configured as a laminated structure with a low resistant conductive layer and a high resistant conductive layer of a wiring circuit (Patent Document 1); and
(ii) a wiring circuit board (printed wiring board) which has a parallel flat plate structure with a power supply layer and a ground layer, wherein the power supply layer or the ground layer is incorporated with a resistivity conductive film and an electronic component current supply pattern and the thickness of the resistivity conductive film is set to 1/10 or less of that of the electronic component current supply pattern (Patent Document 2).
Both the wiring circuit boards of (i) and (ii) suppress the variation in the power supply voltage by connecting a high resistant loss layer (the high resistant conductive layer or the low resistant conductive film) to the power supply layer, losing the high-frequency current (transmission noise) flowing in the power supply layer, and inhibiting the parallel flat plate resonance between the power supply layer and the ground layer.
However, the high resistant loss layer connected to the power supply layer occupies a large area. Since the wiring circuit board of an electronic apparatus is packaged with a high density in effect, a signal transmission line is also present in the vicinity of the power supply line where the power supply layer is circuit-patterned. For this reason, when the high resistant loss layer is disposed to be connected to the power supply line, problems may arise in that the quality of a signal waveform easily deteriorates, such as cross talk in the signal transmission line, delay of signal transmission, or non-exceeding of a threshold value caused due to reduction in a voltage. Accordingly, the wiring circuit boards of (i) and (ii) may not be realized in practice.    [Patent Document 1] Japanese Laid-Open Patent Application No. 2003-283073    [Patent Document 2] Japanese Laid-Open Patent Application No. 2006-49496